Severing bond wire by kinking and twisting

Abstract

An electrically conductive lead is formed using a bonding tool. After bonding the wire to a metal surface and extending a length of the wire beyond the bonding tool, the wire is clamped. Movement of the bonding tool imparts a kink to the wire at a location where the wire is fully separated from any metal element other than the bonding tool. A forming element, e.g., an edge or a blade skirt provided at an exterior surface of the bonding tool can help kink the wire. Twisting the wire while tensioning the wire using the bonding tool can cause the wire to break and define an end. The lead then extends from the metal surface to the end, and may exhibits a sign of the torsional force applied thereto.

The invention claimed is: 
     
       1. A method of forming an electrically conductive lead of a component, comprising:
 using a bonding tool to bond a wire extending beyond a surface of a bonding tool to a metal surface; 
 drawing the bonding tool away from the metal surface while allowing the wire to extend farther from the surface of the bonding tool; 
 clamping the wire to limit further extension of the wire beyond the surface of the bonding tool; 
 moving the bonding tool while the wire remains clamped such that the bonding tool imparts a kink to the wire at a location where the wire is fully separated from any metal element other than the bonding tool; and 
 twisting the wire and tensioning the wire using the bonding tool such that the wire breaks at the kink to define an end, wherein the lead comprises the wire extending from the metal surface to the end. 
 
     
     
       2. The method as claimed in  claim 1 , wherein the twisting of the wire comprises imparting relative rotational motion between the bonding tool and the metal surface about an axis in a direction of a length of the wire. 
     
     
       3. The method as claimed in  claim 2 , wherein the relative rotational motion is motion of less than or equal to one full rotation. 
     
     
       4. The method as claimed in  claim 2 , wherein the relative rotational motion is motion of less than or equal to one full rotation, the relative rotational motion repeated up to ten times. 
     
     
       5. The method as claimed in  claim 2 , wherein the end of the wire has diameter in all directions which is smaller than a diameter of the wire at a location between the metal surface and the end. 
     
     
       6. The method as claimed in  claim 2 , wherein the bonding of the metal wire comprises forming a ball bond at a first end of the wire joined to the metal surface. 
     
     
       7. The method as claimed in  claim 6 , wherein the moving the bonding tool is performed such that the wire is moved to within 100 microns of a surface of the ball bond. 
     
     
       8. The method as claimed in  claim 2 , wherein a forming element is provided at an exterior surface of the bonding tool, and the moving of the bonding tool imparts the kink by forcing the wire against the forming element. 
     
     
       9. The method as claimed in  claim 2 , wherein the forming element includes an edge exposed at the exterior surface, the moving of the bonding tool imparts the kink by forcing the wire against the edge. 
     
     
       10. The method as claimed in  claim 2 , wherein the metal surface is a surface of a metal element, wherein the method includes repeating, one or more times: the using a bonding tool, drawing the bonding tool, clamping the wire, moving the bonding tool, and twisting the wire and tensioning the wire, to form a plurality of leads bonded to the metal surface, then forming a dielectric element surrounding individual leads of the plurality of leads, and patterning the metal element to form a plurality of metal features at a surface of the dielectric element, each lead bonded to a feature of the plurality of features. 
     
     
       11. The method as claimed in  claim 2 , wherein the metal surface is a surface of a metal feature of a plurality of metal features at a surface of dielectric structure of the component, and the method includes repeating, one or more times: the using a bonding tool, drawing the bonding tool, clamping the wire, moving the bonding tool, and twisting the wire and tensioning the wire, to form a plurality of leads bonded to metal surfaces of the metal features, then forming an encapsulation surrounding individual leads of the plurality of leads, wherein the ends of the leads are uncovered by the encapsulation at a surface of the encapsulation. 
     
     
       12. The method as claimed in  claim 2 , wherein the drawing the bonding tool is performed while moving the bonding tool away from the metal surface at least partly in a first lateral direction, and then moving the bonding tool at least partly in a second lateral direction opposite the first lateral direction so as to form a first bend in the wire, the first and second lateral directions being parallel to the metal surface. 
     
     
       13. The method as claimed in  claim 2 , wherein the drawing the bonding tool comprises drawing the bonding tool in an upward direction away from a reference plane defined by the metal surface, and the moving the bonding tool comprises moving the bonding tool in a downward direction towards the reference plane. 
     
     
       14. The method as claimed in  claim 1 , wherein the drawing the bonding tool comprises drawing the bonding tool in an upward direction away from a reference plane defined by the metal surface and drawing the bonding tool in a first lateral direction away from the metal surface, and then moving the bonding tool at least partly in a second lateral direction opposite the first lateral direction so as to form a first bend in the wire. 
     
     
       15. The method as claimed in  claim 1 , wherein the drawing the bonding tool comprises drawing the bonding tool in an upward direction away from a reference plane defined by the metal surface, then drawing the bonding tool at least partly in a first lateral direction parallel to the metal surface, and then drawing the bonding tool again in an upward direction away from a reference plane defined by the metal surface, and the moving the bonding tool comprises moving the bonding tool in a downward direction towards the reference plane. 
     
     
       16. A method of forming a component assembly having a plurality of electrically conductive leads, comprising:
 using a bonding tool to bond a wire extending beyond a surface of a bonding tool to a metal feature at a surface of a component; 
 drawing the bonding tool away from the metal surface while allowing the wire to extend farther from the surface of the bonding tool; 
 clamping the wire to limit further extension of the wire beyond the surface of the bonding tool; 
 moving the bonding tool while the wire remains clamped such that the bonding tool imparts a kink to the wire at a location where the wire is fully separated from any metal element other than the bonding tool; 
 twisting the wire and tensioning the wire using the bonding tool such that the wire breaks at the kink to define an end, wherein the lead comprises the wire extending from the metal feature to the end, wherein the twisting of the wire comprises imparting relative rotational motion between the bonding tool and the metal surface about an axis in a direction of a length of the wire; 
 repeating, a plurality of times: the using a bonding tool, drawing the bonding tool, clamping the wire, moving the bonding tool, and twisting the wire and tensioning the wire to form a plurality of the leads, wherein the end of each lead is at least 50 microns from the metal surface to which it is bonded; and 
 forming an encapsulation surrounding individual leads of the plurality of leads, wherein the ends of the leads are not fully covered by the encapsulation at a surface of the encapsulation. 
 
     
     
       17. The method as claimed in  claim 16 , wherein the using a bonding tool is performed such that a ball bond forms where the wire is bonded to the metal surface and the moving the bonding tool is performed such that the wire is moved to within 20 microns of a surface of the ball bond. 
     
     
       18. The method as claimed in  claim 16 , wherein the drawing the bonding tool is performed while moving the bonding tool away from the metal surface at least partly in a first lateral direction, and then moving the bonding tool at least partly in a second lateral direction opposite the first lateral direction so as to form a first bend in the wire, the first and second lateral directions being parallel to the metal surface, and the relative rotational motion is motion of less than or equal to one full rotation, and the relative rotational motion is performed from one to ten times. 
     
     
       19. The method as claimed in  claim 16 , wherein the drawing the bonding tool comprises drawing the bonding tool in an upward direction away from a reference plane defined by the metal surface and drawing the bonding tool in a first lateral direction away from the metal surface, and then moving the bonding tool at least partly in a second lateral direction opposite the first lateral direction so as to form a first bend in the wire.